The present invention relates to the field of communications and more particularly to methods of estimating error rates and related receivers.
In digital communications systems, such as a radiotelephone communications system, a quality of service may be specified in terms of an average frame error rate (FER) or average bit error rate (BER) for information frames received. To maintain a desired quality of service, a transmitter (for either a mobile terminal or a base station) may vary a transmission power level and/or channel/source coding method to accommodate, for example, a desired quality of service, variations in system loading (number of mobile terminals being serviced), and/or variations in channel conditions. An estimation of an error rate for communications received at a receiving device can, thus, be calculated, provided to a transmitting device, and used to vary transmission power.
An error rate can be estimated by averaging a number of bits or frames that fail a cyclic redundancy check. Such an approach, however, may provide a relatively low convergent speed. If an operating frame error rate is 1%, for example, a statistically reliable frame error rate may require observation of at least several hundred frames. During this period, channel conditions could change significantly, which could make responsive adaptation difficult to achieve.
According to embodiments of the present invention, an error rate for received communications can be estimated. In particular, each of a plurality of received symbol sequences can be iteratively processed to provide a respective plurality of data sequences, and a number of iterations performed to provide each of the plurality of data sequences can be provided. An error rate for the received communications can be estimated based on the number of iterations performed to provide each of the plurality of data sequences.